JP-A-11-147901 discloses a kallikrein-kinin system inhibitor which comprises, as an active ingredient, at least one selected from the group consisting of acidic mucopolysaccharides and physiologically acceptable salts thereof, and hyaluronic acid is disclosed as an example of the acidic mucopolysaccharides. In addition, the same document discloses an agent for treating or preventing acute colitis and chronic colitis, which comprises poly-sulfated hyaluronic acid as an active ingredient.
However, the above document does not disclose a test in which hyaluronic acid or poly-sulfated hyaluronic acid was actually administered to an animal of inflammatory bowel diseases, but discloses only an enzymological in vitro test on the inhibitory action of a kallikrein-kinin system. From the viewpoint of technical common sense in the technical field, it cannot be judged based on only such an in vitro test that it is effective for an animal of inflammatory bowel diseases. What is more, since the kallikrein-kinin system is not always considered to be the factor relating to the inflammatory bowel diseases, and other various factors are intricately entangled therein, it cannot be judged directly from the inhibitory activity of a kallikrein-kinin system that hyaluronic acid and poly-sulfated hyaluronic acid have markedly excellent effect on the inflammatory bowel diseases.
Although “an agent for treating or preventing acute colitis and chronic colitis, which comprises poly-sulfated hyaluronic acid as an active ingredient” is disclosed in the same document, the poly-sulfated hyaluronic acid is a substance which is physically and pharmacologically completely different from hyaluronic acid in terms that it has a sulfate group. Accordingly, even when the “poly-sulfated hyaluronic acid” is replaced with “hyaluronic acid”, the agent comprising hyaluronic acid does not always have the same activity as that comprising poly-sulfated hyaluronic acid.
In addition, the above document neither discloses nor suggests the agent for preventing or improving various specific symptoms accompanied by inflammatory bowel diseases (diarrhea, weight loss, bowel tissues edema, cell infiltration, surviving period shortening, and the like), which comprises hyaluronic acid as an active ingredient.